Manufacture of photographic film



Oct, 14, 1941. I G. F. NADEAU 97 I MANUFACTURE OF PHOTOGRAPH'IC FILMFiled Nov. 26, 1940 GELAT/N-CELLULOSE N/TRATE. YZED CELLULOSE ACETATEPROP/ONATE.

N/TRATE.

TR/ACETATE SUPPORT.

GALE E/YADEAU IN V EN TOR by MW Patented Oct. 14, 1941 UNITED, STATESPATENT OFFICE I assess: monomer or rnorocaarnro .rmu

Gale F. Nadeau, Rochester, N. Y., assignor to EastmanKodak Company,Rochester, N. Y., a

corporation of New Jersey Application November 26, 1940, Serial No.367,179

3 Claims. (01.95-9) This invention relates to photographic materials andmore particularly to the production of photographic film having acellulose triacetate base or support and possessing the degree offlexibility and emulsion adherence r quisite for photographic was.

As is well how, commercial cine and other types of photographic filmhave largely been manufactured from cellulose nitrate, since this hasbeen found to involve many difllculties in casting the film, recovery ofthe solvent due to its extreme"volatility, and the like. Nevertheless,films have been made from cellulose triacetate '5 and have proved to behighly satisfactory and, as previously stated, not only equivalent, buteven superior to cellulose nitrate as film support,

particularly cine support. However, due to the extreme 'insolubility ofcellulose trlacetate in.

particular cellulose ester has certain physical 1,0 ordinary-solvents,it has been extremely dimcult properties of strength, rigidity,durability and toughness which enable it to withstand relatively severeabrasive, flexing and other influences it \must undergo in modernmotion-picture apparatus and when employed forother purposes. Cellulosenitrate, however, has certain inherent drawbacks which make itunsuitable for many purposes, chief among which is its relatively highinflammability. With the advent of the amateur moving picture, it (W88necessary to provide 'a material whichiwas safe to handle and, if notentirely uninfiammable, was nevertheless slowburning. The answer to thisproblem-was found in the cellulose organic acid esters, particularlycellulose acetate, and more recently in the cellulose mixed organic acidesters such as cellulose acetate propionate and cellulose acetatebutyrate,

all of which are relatively slow-burning materials photographic films.However, none of these cellulose organic acid ester materials havemeasured 'up to cellulose nitrate in all respects, the

latter having been found to possess superior and v 35 compromise betweenemulsion adherence and unique qualities of strength, rigidity,toughness, durability and flexibility. I

a The cellulose acetate heretofore employed in safety cine film has beenof theincompletely esterfied variety, that is, cellulose acetatecontaining from 41% to 41.5% acetyl. For some time it hasbeen known thatthe fully esterfled ester, namely, cellulose triacetate, possessedphysical,

properties which were substantially equivalent to those ofcellulosenitrate without at the same time having the disadvantages inherent inthe latter material. Howevencellulos'e triacetate has been an extremelydlflicult material to deal with in the manufacture of photographic filmsupport for the reason, among others, that noneoi the ordinary celluloseester solvents such as acetone, methyl alcohoLethyl alcohol, ethylenechloride and other liquids are solvents for the tri-ester. Methylenechloride, a highly volatile andrelatively ea:-

pensive material has been found to be about 'the if not impossible, toprepare this type of film for I the application of a photographicemulsion because of the problems involved in subbing, that is, preparingthe film and thereby giving it the proper flexibility andbrittleness-characteristics.

herence. If the'sensitized emulsion is caused to adhere to thefilmsupport too strongly, or in fact, if any layer deposited on the film iscaused to adhere too strongly, the film becomes brittle and subject torupture underonly a slight amount of flexing. Qn the other hand, ifthedegree of adherence oithe emulsion or any of the uh- I derlying layersbetween the emulsion and the film support is lowered, excessivestripping of the emulsion from the support will occur, that is, the

3 0 emulsion will tend to loosen and break away from the support. L Thisseparation of the emulsion or other layers may extend for a considerabledistance longitudinally of the film. It will thus be seen that it ,isalways necessary to workout a and flexibility (brittleness). This isalways an merits and on the basis of the particular uses to 40 which itis-ultimately to be put in practice.

The present problem, the solution ofwhich is provided by the instantinvention, derives from the use of cellulose triacetate as a filmsupport material. This invention has as its principal object to providea means of employing cellulose triacetate as a photographic filmsupport. A further obiectis to provide a methodwhereby this type of.film support'ca'n be satisfactorily subbed and prepared for theapplication ooi a photographically sensitive colloid layer to produce afinished film which will haveisatisfactory' flexibility, i. e., will besuflidlently free from brittleness, to enable it to be processedcommercial cine film and for other only practical solvent for thisester, but its use Other objects will appear hereinafter.

. nitrate and These objects are accomplished by the following inventionwhich, in its broader aspects, comprises the application to a cellulosetriacetate film support of a cellulose nitrate layer, applying over ,thecellulose'nitrate layer a layer of hydrolyzed cellulose \mixed organicacidestersuch as hydrolyzed' cellulose acetate propionate, applyingoverthe hydrolyzed layer a layer composed of gelatin mixed with a smallamount of cellulose thereafter applying over the last mentioned layerthe sensitive colloid layer.

In the following examples and description I have set forth several ofthe preferred embodiments of my invention, but they are to be regardedmerely as illustrations and not as a limitation thereof.

In the single figure of the accompanying drawing there is illustrated ingreatly exaggerated scale a cross-section of a typical photographic filmproduced in accordance with my invention.

In carrying out extensive research on the problem of suitably preparinga cellulose triacetate film support for the application of thesensitized emulsion, it was found that the material could not be dealtwith on the same'basis as with other photographic film support,primarily because of the fact that the ordinary solvents do not attackthe cellulose triacetate surface and therefore it was impossibleproperly to secure the sub-layer to the support by penetration of thesolvent medium into the material of the support. In the course of mystudy of this problem I have determined that a material must be employedwhich possesses a certain amount of chemical unsaturation within itsmolecule, that is, a material which will have a natural afiinity forcellulose triacetate. As will be readily appreciated, in the cellulosetriacetate aggregate there ar no free hydroxyl groups, all esterlfiablehydroxyl groups of the glucose unit having been esterified-by the acetylradical, thus producing a completely esterifled compound which is highlyresistant to the wetting or penetrating action of ordinary solvents.

Notwithstanding these difllculties, I have found that if one employs asolution of cellulose nitrate dissolved in an appropriate solvent orsolvent mixture, such as a mixture of methyl alcohol and acetone, a thinlayer of the nitrate may be adhesively attached tothe cellulosetriacetate surface. This attachment takes place, not by any penetrativeaction of the solvent but merely by virtue of the chemical attractionexisting between the cellulose nitrate and the cellulose triacetate.Thus, the nitrate is joined to the cellulose triacetate by the action ofchemicai'or adhesive forces analogous to those existing between aresinous or other priming coat deposited on a metal surface prior to theapplication of a lacquer or when an adhesive is applied to a glasssurface.

Assuming the cellulose tria'cetate support to have been satisfactorilysubbed with a thin layer of cellulose nitrate in the manner justspecified,

' there is still the problem of adhesively joining the sensitizedgelatin layer to the subbed material to obtain a film of satisfactoryflexibility and freedom from brittleness. I have found that if thecellulose nitrate layer is subbed with a solution of a hydrolyzedcellulose organic acid ester, the layer of the material deposited afterevaporation of solvents will be of such nature that, not only will it bepermanently and adhesively joined to the underlying cellulose nitratelayer, but will also be of such nature as will permit ofthe-apgfiication'of the necessary gelatin sub to provide the propersurface for application of the final emulsion layer.

The gelatin sub is preferably a mixture of gela-' tin and cellulosenitrate, the nitrate being present in a small amount, but suflicient toincrease the afiinity of the gelatin sub for the cellulose organic acidester underlying it. It might be said in this connection that thecellulose organic acid ester material of the underlying layer ishydrolyzed for thepurpos of making it more compatible with the gel subwhich is superimposed thereon. The sensitized gelatin layer can then bereadily deposited on thegel sub surface and a satisfactory filmproduced.

It will be seen from the above discussion that a number of extremelydelicate problems are presented in the manufacture of a practicalphotographic film if one employs a cellulose triacetate support and itis only by means of the specific combination of layers above set forththat a satisfactory product can be produced. Y

My invention will be more fully, illustrated by reference to severaltypical examples describing the subbing and emulsion-coating ofcellulose triacetate film support.

Example 1 A cellulose tria'cetate film support of .005 inch in thicknessis subbed by applying thereto a solution of an alcohol-soluble cellulosenitrate having the following composition.

Per cent by weight Cellulose nitrate 3 Acai'nnp 22 Methanol Hydrolyzedcellulose acetate propionate (648% and preferably 10-12% acetyl)--- 2Ethylene chloride 10 Ace 35 Monomethyl ether of ethylene glycol 25Methanol 28 After evaporation of solvents the hydrolyzed celluloseacetate propionate surface is then subbed with a layer of gelatin whichis deposited from a solution of the following composition:

Percent by weight GPlaHn 1 Cellulose nitrate (alcohol-soluble) 0.2Acetnne 50 Water 8 Methyl alc 38.8

Acetic Acid 2. 0 i

The cellulose nitrate content of the solution may range from .1%' to .4%while the solution may also contain 1-5%, based on the weight of thegelatin, of a gelatin hardener such as chromic chloride, for example.After the gel sub-,

bing operation has been completed in accordance with standard practice,a sensitive gelatinosilver halide cine-positive emulsion is applied tothe subbed surface of the film, and subjected to sweeper Example Y Acellulose triacetate cine support was subbed a convenient size, weinches wide by: 40 inches long, is held at one end with both hands withthe emulsion side toward the operator and is then torn lengthwise withsuccessive quick motions of one hand, the tearing generally beingcarried out at a slight angle to the edge of thestrip in order to obtainan oblique tear. tears thus produced are more or less Jagged. An attemptis now made to pull back the emulsion coating from as in Example 1 withcellulose nitrate. l ollowthe film with the fingernails andthe degree toing the application of the nitrate sub there was applied thereover ahydrolysed cellulose acetate butyratesub from a subbing solution havingthe following composition 4 Percent by weight Hydrolyzed celluloseacetate butyrate 042% butyryl) p .2 Ethylene chloride l0 Acetone 35Monomet hyl ether ofethylene glycol- Methanol 28 A hardened gelatin sub.was applied over the cellulose acetate butyrate as in Example l,i'ollowed by application 'of a gelatino-siIver-halide emulsion. Thisfilm was then subjected to the flexibility (brittleness) and dry and wetstripping tests and was found to be satisfactory in all respects,

- The subbing operation per se may be carried out inany-convenientmanner, preferably by means of an applicator roll dipping in the sub?bing solution and then continuously brought in contact with the filmsurface. Other equivalent means of subbing the supportwell known tothose skilled in he art may be employed, if desired.

As will be understood, many changes maybe made in the above formulae.and in the technique of applictaion of the subs within the scope of myinvention. However, in each instance, I

employ a fully esterified. celluloseacetate (celluwhich the emulsionseparates from the support is a measure of its adherence. 'It will, ofcourse, be understood/ that the standards of emulsion adherence willvary for diflerent types of film and what'is considered satisfactory foronefilni .may not be satisfactory for another. For example, stripping(emulsion adherence) is said to be satisfactory of X-ray film if theemulsion cannot be stripped back more than one or twoinches.

For cine film,- on the other hand, there should besiderable force withthe balls oi the fingertips for several seconds. -A film is said to havesatisfactory wet stripping (emulsion adherence) properties when nopeeling, or substantially no peel- .in of the emulsion occurs asa'result of this rubbing action. Wet stripping is said to beunsatisfactory when an appreciable or large amount lose triaoetate) supprt. a cellulose nitrate sub, a

hydrolyzed celluose organic acid ester sub, and a hardened gelatin subin the order named, since,

only bythis specific combination of layers can the best results beobtained and a commercially of the emulsion comes on. For most types offilm it'should not be possible, to remove'pieces wider than Y ln hbythia'te'st.

The brittleness test is carried out as follows: A; strip of film ofconvenient size is heated for forty-five minutes in a brittleness ovenin which air having; a controlled relative humidity of 20-25% and atemperature 01410-120 1. is circulated. The film is then removed fromthe satisfactory photographic filmsbe produced. If

- it is desired'to employcellulose acetate as the hy- 'b td layerbetween the nitrateand the hardened gelatin sub, a cellulose acetate ofabout 70% precipitation value and containing about 38% aeetyl may bedeposited from a 3% solution of 70% acetone and 80% methyl alcohol. I

As is understood by those skilled in the art the term "sub" referstolayers of extremely minute thickness deposited onthe surface of the filmsupport. For cine tyndsiof film having a thick,

ness of the order'of .Qtitjjinch, each of the subs, with the exceptionalthe gel sub, may have. a

oven and folded at ten different places along the strip by pressing thefoldsuddenly between the forefinger and the thumb. If the film isbrittle,

' this sudden folding'will cause it to break or snap thickness of aboutl'to 3% of the thickeness of the support itseli', .that is, of the orderof-.0i )005' minute, but of the order of'about 'l0% of the thickness 'ofthe other subs.

As indicated above, the photographic films of inch. The thickness'hfthegel sub is even more has a satisfactory dry stripping test. My inventionwill my invention are found to 'fully meet the requirements oicommercial use and to "respond successfully'to the standard flexibility(brittleness). W i and-dry stripping and theso-called The dry strippingtest is carried out as follows:

A piece of the complete film of 7 5 gelatinoesilverhalide,

' heater-after" tests, Thesetests will now bede- -.scribedasfollows:

in two atthe fold. The flexibility maybe defined in terms of freedomfrom brittleness which may be figured directly in percentages from theresults ofth'e test. For example, a film issaid to -be free frombrittlenessif it ruptures'at only four out of ten folds.

The f ter -after" test is carried out simply by running thefinishedfilm, after processing in the photographic developing baths usuallyemployed and subsequently drying the film and then subjecting it to thesame steps as are employed in the dry strippingitest; A film is said tohave satisfactory heater-after" stripping if it re- -sponds in the samemanner-as does a film which y further understood by reference to thesing e figure of the drawing in which A designates a cellulosetriacetate film support, 13 a cellulose nitrate sub adheslvely Joined tothe support, C a hydrolyzed cellulose acetate propionate layeradhesively Joined to the cellulose nitrate layer, D a hardenedgelatin-"- cellulose nitrate layer.-; and n is the sensitive emulsion.

What I claim and desire to secure by Letters Patent oi' the UnitedStates is: 4

1. A photographic film of satisfactory 'ilexibility and free frombrittleness which comprises a cellulose triacetate support 'and aphotographically sensitive colloid layer joined to the support by acomposite intervening layer comprising a cellulose nitrate subadhesively joined to the support, a hydrolyzed cellulose mixed organicacid'ester sub adhesively joined to the cellulose nitrate sub and amixed gelatin cellulose nitrate sub adhesively Joined to the cellulosemixed organic acid ester sub. said intervening layer renderingthetlexibility characteristics of the film as a whole independent" orthe degree of adherence existing between the photographically sensitivelayer and the subbed support.

2. A photographic fllm of satisfactory flexibility and free frombrittleness which comprises a cellulose triacetate support and aphotographically sensitive colloid layer joined to the support by acomposite intervening layer coniprising a cellulose nitrate subadhesively joined to the support, a hydrolyzed cellulose acetateaaeaee'i propionate sub adhesively joined to the cellulose nitrate suband a mixed gelatin cellulose nitrate sub adhesively joined to thehydrolyzed cellulose acetate proplonatesub, said intervening layerrendering the flexibility characteristics of the illm as a wholeindependent of the degreeot adherence existing between thephotographically sensitive layer and the subbed support.

3. A photographic'lllm of satisfactory flexibility and free frombrittleness which comprises a cellulose triacetate support and aphotographically sensitive colloid layer Joined to the sup port by acomposite intervening layer-comprising a cellulose nitrate subadhesively joined to the support, a hydrolyzed cellulose acetatebutyrate sub adhesively Joined to the cellulose nitrate sub and a mixedgelatin cellulose nitrate sub adhesively joined to the hydrolyzedcellulose acetate butyrate sub, said intervening layer rendering theflexibility characteristics of the illm as a whole independent or thedegree of adherence existing between the photographicallysensitive layerand the subbed Supp rt.

GALE F. NADEAU.

